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Frequently Asked Questions

Contact us if you cannot find an answer to your question. Reach us 8:00 am to 4:30 pm Pacific time, business days.

PML products are designed, manufactured and shipped from California.

Product Information

PML designs and manufactures all products in the USA. We are located in Inglewood, California, near Los Angeles.

Extra oil provides additional cooling for the transmission and differential under stressful conditions. Heat buildup, the chief nemesis of a transmission, causes the oil to lose its lubricating properties. Break down of the oil leads to increased wear on the clutches, bands, and seals. The end result is costly premature rebuilds and lost time. Our covers and pans feature raised cooling fins in addition to the increased fluid capacity to reduce oil temperatures. Customers have reported temperatures 20 to 30 degrees cooler. Drain plugs are included on all covers and pans to make oil changes easy.

See our web page on Finishes and Construction.

Because the floor of our deep pans for these vehicles is further away from the valve body than the stock pan, our deep pans feature fingers that are part of the floor of the pan which rise up to the height of the stock pan and hold the filter. The advantage of this design is that it allows you to have the cooling of additional oil capacity while using the readily available stock filter.

Some have asked whether this arrangement will end up leaving a stagnant layer of oil in the bottom of the pan that does not get used. There is plenty of mixing going on with oil being sucked out by the filter, returned from the oil cooler, and the movement of the vehicle that this is not the case. With most of the larger transmission pans the perimeter of the pan is so big that the floor only needs to be dropped an inch to an inch and a half to gain 4 quarts of additional capacity.

If in the future you find a deeper filter that you want to use, the filter support fingers can easily be ground down to the proper height for your new filter.

PML recommends cork or cork composite gaskets or paper gaskets with our products. On some transmission pans and differential covers, RTV or a silicon gasket maker is also a great choice.

A gasket is a seal between two or more surfaces to prevent leaks between the joined objects. When two surfaces are joined, the gasket can deform and tightly fill any spaces so there is no leaking. A soft, flexible gasket works best with the thick, machined flanges of the PML cover or pan and the mounting surface.

If needed, a little bit of spray adhesive or a small smear of silicon sealant can hold the gasket in place during installation.

If your motorhome is newer than 1990, it should have a 4 speed automatic known as the 4L80E. We recommend our part #9167 early style deep pan for this application. Look carefully at the back of the pan to see if you have clearance for a deeper pan. Often the leading edge of the frame cross member that holds the rear transmission mount sticks far enough forward to make access to the rear bolts on the pan difficult. If this is the case on your vehicle, you will have to remove a semi circular piece of material 2" wide by ½" deep in order for our pan to fit. This modification has been done by many others before you. It works and is relatively easy.

If your motorhome is a 1990 or older, it should have the 3 speed Turbo 400 transmission. We make a deep transmission pan, part number 9683, for this transmission. It is the same depth as the OEM truck pan which is likely on your vehicle. The advantage of our pan over stock would be the drain plug, cooling fins, and resistance to leaking. As with the later motorhomes, look carefully at the rear of the pan and the frame crossmember. If your pan has a beveled edge to clear the frame, our pan will not fit.

We are unaware that this is an issue with our 700R4 transmission pans. Typically if something is not a direct bolt on we hear about it. We have heard about the need in certain applications (not specifically 700R4) to modify the leading edge of frame crossmembers, shift cable brackets, and some aftermarket exhaust pipes to make room for our bigger pans.

On 700R4 & 4L60E transmissions there are several orientations for the shift cable bracket. If your shift cable bracket mounts using 2 of the pan bolts, and hangs down alongside the pan, you will have to modify your bracket. Our pan is approximately .150" thicker than stock and will require some material be removed from the bracket in order to prevent contact with the side of the pan before the bolt holes line up. We have literature that describes in words and pictures how this is done that we will be happy to supply if you need it.

If your shift cable bracket mounts on the transmission case above the pan there will be no modification needed.

Our drain plug is a standard ½" diameter by 20 threads/inch magnetic type. It is sealed with a copper washer. When installed in one of our pans, the head protrudes 0.400" beyond the edge of the pan.

Our drain plugs are magnetic to catch any bits of metal in the transmission or differential oil.

We provide on this website, the general dimensions, and a 4 view drawing of each part so you can visualize the shape and size of our products. If you have looked at these and you still need additional information, feel free to give us a call.

PML auto products typically feature walls 5 times as thick as most stock parts (5/32 inch vs. 1/32 inch) and a gasket flange 12 times thicker (3/8 inch vs. 1/32 inch). Stock parts are a thin wall stamped steel construction. They bend, twist, dent, and puncture easily. PML thick wall castings are very stiff and will actually strengthen your transmission case or differential housing.

The gasket flange on thin wall stamped steel parts is very easily deformed. All it takes is a slight over tightening of the mounting screws to bend the flange. Once this happens the part is guaranteed to leak. Our gasket flange is precision machined on a vertical mill to ensure a flat and smooth gasket surface. The thick gasket flange is very stiff and will not deform even if grossly over tightened.

Aluminum is a metal that provides a high strength-to-weight ratio and provides for good heat transfer so our pans are strong and help cool your oil. Sand-casting is the process of pouring of molten metal into a mold to create one thick, solid part.

Sand-casting is a manufacturing technique where a tool (which is the part constructed out of wood or plaster) is sandwiched between two rectangular boxes. Sand is packed into the boxes. Click here to see a picture of a differential cover tool. The result is a big block of special sand with a hollow area inside which looks just like the negative of the part.

Molten aluminum is then poured through passageways in the sand which lead to the hollow area inside the block. The aluminum is allowed to cool and solidify. Once cool, the boxes are removed and the sand is broken away from the aluminum. The result is a raw part which looks just like the finished part but without any of its machined features (mounting holes, gasket flange, drain/fill holes for example).

Sand-casting allows for a one piece part with more complex shapes & features than die casting which reduces the need for machining and welding.

Many other covers and pans are die-cast or stamped. Stamped parts are thin. Also, many believe that sand-cast parts more closely replicate an original, classic look than die-cast or stamped parts.

Fluid temperatures depend many variables: vehicle configuration, the driving conditions, weather, the stress on the transmission. It also depends on where the temperature is checked. Some customers report temperature drops only when they are towing or hauling. Many report quicker recovery to lower fluid temperatures also. The average customer reports a 10 to 20 degree drop. However, because of all the variables, there's no guarantee.

Fluid temps that are too low are also bad. If you are in a sub-zero climate, you might need a warmer.

If your temperature was normal before installing a PML pan, it could be similar after because that is the optimum operating temperature and the system will keep the fluid at that normal temp. "Normal" varies with the transmission, but a common range is 160 to 190 degrees.

If your temperature is still too high, verify the fluid levels. Consider adding a transmission cooler. Change your fluid often. Call your mechanic or transmission shop.

To install a PML differential cover or transmission pan, you will need a torque wrench. The Installation instructions provided with the part give the torque specifications.

Reference this: Tightening Bolts YouTube Video by Wilson Auto Repair.


PML does not offer custom engraving. Try asking a local auto body shop or rebuilder for a recommendation.

Our return policy allows for returns or exchanges within 30 days with a 20% restocking fee. After 30 days, no refunds or exchanges are allowed. So if you return the part to us in as new condition, you will be given a credit for the purchase price minus a 20% restocking fee. You will not get a refund for the shipping to you and will have to pay the shipping to get the part back to us. If you modify or damage the part it will not be returnable. All special order sales are final. Machining is not refundable.

Why Should You Buy a PML Transmission Pan?

  • Cooling
  • Easier maintenance
  • Strength
  • Leak free seal
  • Hardware

Transmissions and transmission repairs are expensive and heat is the biggest enemy of the transmission. Automatic transmissions use oil to shift gears. If the transmission oil gets too hot, it breaks down and the result is a damaged transmission or a transmission that has a shorter life. A PML transmission pan has helps cool transmission fluid in these ways:

  • Extra fluid capacity. If there is more oil in the transmission, there is more oil to absorb heat. Most PML Pans have extra capacity. A few pans have stock capacity to maintain clearances.
  • Aluminum construction. Aluminum conducts heat quickly so that heat is transferred from the oil to the air. Most stock pans are steel and aluminum has a much higher heat conductivity than steel.
  • Fins. Fins increase the surface area of the pan so there is more area for heat transfer out of the oil into the air.
  • Boss for temperature sensor. To monitor the transmission fluid, some folks install a temperature sensor. Since most people do not use a temperature sensor, PML does not machine a hole for a sensor on every pan. There is a boss where a hole can be machined. PML can do the machining (extra cost) or you can machine it yourself or take it to a local machine shop. The boss accommodates various size gages from 1/8 to ½ inch NPT. Some other aftermarket pans are pre-drilled with a particular thread size, which adds cost for those who do not use a sensor and maybe the wrong size for those who do.

When high temperatures cause transmission fluid to lose its ability to lubricate, wear and tear on the transmission increases. If the temperature gets above 250°F, the rubber seals harden then leaks start to occur. ATF manufacturers suggest that for every 20° above 175°F, the life of the transmission is reduced by half. Keeping the transmission cool is especially a concern for vehicles in harsh driving conditions such as towing or hauling, climbing hills, and repeated shifting.

A common question people ask is how much lower will the fluid temperature be with a PML pan. We don't know. Everyone has specific driving conditions and there is a huge variety of vehicles. It isn't feasible for us to test so many vehicles and configurations. Customers that have temperature sensors have reported 10-20 degree (F) drops in oil temperatures. There's no guarantee. If your transmission oil is looking brown or smells burnt, it's getting too hot. An aftermarket pan is an easy and inexpensive way to cool.

A PML transmission oil pan has a drain hole and plug so the fluid can be easily drained. A drain hole makes changing the transmission fluid easier, saving you time. And if you decide to change the fluid yourself, you save money. Draining and replacing the fluid at regular intervals extends the life of the transmission.

The plug included with the transmission pan is magnetic. The magnetic drain plug traps metal particles in the fluid which can cause wear.

The thick wall sand-cast aluminum construction adds strength to the transmission case. Fractures in the transmission case and bell housing are not uncommon from vibration, a failing mount, an internal failure... Here is a story from one of our customers, Sharadon Performance:

"Obviously it (the transmission) had a bad leak. But... he drove it another 2500 k (Canada) including the drive to the shop 1300 k... When I got under the truck I noticed the crack. So I pulled it out. Put it on a engine stand to hold it upright. Pulled the pan off, the crack got bigger... pulled the valve body... The trans fell apart. I know the PML pan made this possible. The stock pan would never have held up to this."

The gasket flange on a transmission pan is precision-machined and thick. It will not bend when bolts are tightened. And the surface is machined completely flat. So a PML transmission pan provides a secure, leak free seal. The thick flange is intended for use with the cork, rubber cork or similar gaskets.

Usually PML does not recommend using an expensive reusable gasket with a PML pan. These gaskets are intended for use with thin stock pans which flex when the bolts are tightened and conform to the reusable gasket. A PML pan will not flex at all. The thick rubber on the reusable gaskets is easily damaged, causing a leak. The May 2012 issue of Transmission Digest has an article about reusable gaskets. For some transmissions, the factory gasket or the only available gasket is the resusable kind. Our pans will work fine with these, just be careful that the gasket is clean and free of nicks.

Mounting hardware and a drain plug are included with the transmission pan. If you have PML machine a temperature sensor, a plug for the gage will also be included.

Stock bolts will not work since the flange is much thicker. Some aftermarket pans do not include the mounting bolts, so you have to order them separately or make a quick trip to the hardware store. Hopefully before you removed your stock pan.

PML designed its transmission pans to use the stock filter. You can get these inexpensively and easily. PML does not design pans that require filter extensions since these add an extra location that can fail and leak and add cost.

  • Increased oil capacity (most pans), aluminum material, and raised fins for cooler oil temperatures
  • Boss cast into pan can be machined for various size temperature sensors
  • Magnetic drain plug for easier maintenance
  • Thick wall sand cast construction to add strength to the transmission case
  • Machined gasket surface with a thick flange for a secure seal
  • Mounting hardware provided
  • Works with stock filter, no special parts required
  • Designs for cars, trucks, SUVs, and motor homes
  • Available in as-cast aluminum, black powder coated, and polished finishes

PML does not feature our logo or name on our pans, just solid design and construction.

Learn more about finishes and construction of PML parts.

Keep it cool, keep it clean, keep it alive.

PML Differential Covers

PML differential covers feature:

  • Increased oil capacity and raised fins for cooler oil temperatures
  • Made from aluminum for better heat transfer than steel
  • Magnetic drain plug allows oil changes without removing the cover
  • Machined gasket surface for secure seal using RTV or factory reusable gasket
  • Thick wall sand cast construction to add strength to the differential housing
  • Thick gasket flange will not bend when bolts are tightened
  • Mounting hardware provided
  • Available in as-cast aluminum, black powder coated, and polished finishes

There are many reasons to buy a PML differential cover. Although the features depend on the application, the short of it is that a PML diff cover will save you time and money. We design covers with oil fill, level check and drain holes to make oil changes easy. Changing the oil at regular intervals is the best thing you can do for the life of your differential.

High temperatures cause oil to lose its ability to lubricate, increasing wear and tear on the differential. This is especially a concern for vehicles in harsh driving conditions such as towing or hauling. The extra oil capacity, raised fins, and aluminum construction of PML differential covers help reduce oil temperatures. The magnetic drain plug traps metal particles in the oil to further prevent wear.

PML rear and front end diff covers also feature precision-machined 3/8-inch thick gasket flanges for a leak free seal. The thick wall sand-cast aluminum construction adds strength to the differential housing. Many covers feature a boss that can be drilled and tapped for a temperature sensor. Mounting hardware (bolts, washers, plugs) is included.

Finally, PML covers look great. We offer a choice of finishes: natural as-cast, black powder coated with shaved fins, or polished. PML does not feature our logo or name on our covers, just solid design and construction. Learn more about finishes and construction of PML parts.